Conventionally, as disclosed in patent document 1, an in-vehicle communication apparatus is known in which an antenna located at a physically remote place is connected to a wireless communication device that performs a wireless communication through the antenna with a coaxial cable. When a transmission amplifier of the antenna is physically separated from a wireless communication device that supplies a driving power of the transmission amplifier through the coaxial cable, a transmission output of the antenna is affected by a loss of the coaxial cable.
The inventors of the present application have found the following regarding an in-vehicle communication apparatus. As a method of regulating the transmission output of the antenna taking an effect of the loss of the coaxial cable into account, a technique may be considered in which a result of detecting an output signal of the transmission amplifier by a detector is output to the wireless communication device and, based on the detection result, a power supplied to the transmission amplifier is regulated in the wireless communication device so as to obtain a predetermined transmission output.
When the detector is used in an in-vehicle communication apparatus in which an antenna module and a wireless communication device, which are located at places physically separated from each other, are connected through a coaxial cable, costs such as a financial loss, an labor may increase. Incidentally, the antenna module includes the antenna and the transmission amplifier.
When it is necessary to regulate the transmission output of the antenna in the in-vehicle communication apparatus after mounted to a vehicle, not only the detector but also a dedicated vehicle harness that feeds back the detection result from the detector to the wireless communication device may be required to be mounted to the vehicle. This may cause an increase in the financial loss or the labor. In addition, a method of correcting the transmission output of the antenna may be prepared for each vehicle or each vehicle model. Thus, in this case, the financial loss or the labor may increase.